An MTC or Cellular Internet of Things (CIoT) technology is a combination of wireless communications and information technologies, is used for bidirectional communication, and is applicable to fields such as security monitoring, vending machines, freight tracking, and meter reading. According to communication objects, MTC may include three communication modes, machine-to-machine (M2M), machine-to-mobile terminal (for example, remote monitoring by a user), and mobile terminal-to-machine (for example, remote control by a user). The MTC is an important application in a future communications field, and future MTC may mainly include smart metering, medical detection, logistics detection, fire detection, wearable device communication, and the like. It is predicted that a quantity of connected MTC devices will reach 50 billion by 2022.
Currently, two main core network architectures in third generation partnership project (3GPP) are a Gb-based architecture used in Global System for Mobile Communications (GSM) and General Packet Radio Service (GPRS) networks and an S 1-based architecture used in an long term evolution (LTE) network, and the two architectures have respective advantages and disadvantages. Therefore, both the Gb-based architecture and the S 1-based architecture should be compatible as much as possible in a new MTC access network. Therefore, discontinuous reception in an air-interface connected mode needs to be supported in a new MTC access network design. In the S 1-based architecture, because there is a connection between a base station and a core network, and an access stratum (AS) (in an idle mode and a connected mode) and a non-AS (NAS) (in an idle mode and a connected mode) of UE are consistent, no problem occurs. In the Gb-based architecture, an air interface mode is not maintained by signaling to a core network device. Instead, a ready timer between a core network device and a base station is set and an AS timer (AS timer) that is between a base station and the UE and that controls an air interface mode is maintained. Therefore, in the MTC access network design, a ready timer that controls the core network device to send data to the base station is maintained between the core network device and the UE, and an AS timer that controls the air interface mode is maintained between the base station and the UE.
Compared with a conventional service, an MTC service has some new characteristics. For example, a time for sending the MTC service is usually quite long. Consequently, a time for sending by UE on an air interface is quite long, further, there may be a conflict between a ready timer between a base station and a core network device and an AS timer between a base station and the terminal, and therefore, the core network device cannot directly send a downlink data packet to the UE. In a case, the ready timer does not expire, and in this case, the core network device directly sends the downlink data to the base station. However, in this case, because the AS timer between the base station and the terminal has expired, an air interface of the UE has been released, the UE is in an air-interface idle mode, and the base station cannot schedule the UE and send the corresponding downlink data packet. In another case, the ready timer expires, but the AS timer does not expire. Because the ready timer expires, when the core network device needs to send the downlink data to the UE, the core network device does not directly forward the data to the corresponding base station. Instead, the core network device sends a paging request, and the base station sends a paging message. Because the AS timer does not expire, the UE is still in a connected mode, the UE listens only to scheduling that is based on a Cell-Radio Network Temporary Identity (C-RNTI) of the UE, and the downlink data cannot be sent to the UE using the base station.